AM1 (RHF) type semiempirical quantum chemical calculations have been applied to cyclacenes whose fusion points and peri positions of one of their peripheral circuits are substituted with nitrogen and boron, respectively. The structures have been found to be stable but endothermic (except for R = 8 and 9) in nature. The nitrogen and boron (the fusion points peri positions, respectively,) substitution have been found to have stabilizing effect on the parent unsubstituted cyclacenes. Some geometrical and physicochemical data are also reported. (C) 2004 Elsevier B.V. All rights reserved.